Defrosting of evaporator



ct. 9, 1956 G. MUFFLY 2,765,633

DEFROSTING OF EVAPORATOR Filed Aug. 9, 1950 5 Sheets-Sheet l M6" i/AM Y ar/14 DEFROSTHNG F EVAPORATOR Glenn Muiily, Springfield, Ohio Application August 9, 1950, Serial No. 17 8,498 6 Claims. (Cl. 62-1173) This invention relates to improved household refrigerators, and more particularly to improved defrosting means for such refrigerators.

One object of the present invention is to provide a refrigerator having a frozen food compartment and a separate non-freezing compartment, each with its own evaporator, with means for defrosting of the freezer evaporator without heating the evaporator of the warmer compartment.

One object of the present invention is to provide a refrigerator having a frozen food compartment and a separate non-freezing compartment, each with its own evaporator, with means for defrosting of the freezer evaporator without heating the evaporator of the warmer compartment, and while the evaporator of the warmer compartment continues to absorb heat from the space it cools.

In the drawings:

Fig. 1 is a sectional view of a household refrigerator incorporating the features of this invention.

Fig. 2 is a front elevation of Fig. 1, omitting the front door of the cabinet.

Fig. 3 is a horizontal section of Figs. 1 and 2 on the lines 3-3 thereof.

Fig. 4 is a diagrammatic illustration of a refrigerating system suitable for use in connection with Figs. 1, 2 and 3 and illustrating an arrangement of values which provide for hot-gas defrosting of the freezer evaporator.

Fig. 5 is a diagrammatic illustration of a modified electrical circuit for defrosting the freezer evaporator.

Referring to Fig. l the ice maker is seen in section and will be recognized as operating upon the same principle as other floatation type ice makers disclosed in my several issued U. S. patents and pending patent applications. The evaporator coil is soldered or otherwise secured to a number of metal buttons 12 preferably made of copper or other metal having a high thermal conductivity. These buttons occur at intervals along the length of the evaporator tube and are soldered or otherwise secured to the vertical wall 14 which forms one side of the ice maker tank 16. During operation of this ice maker water is circulated upwardly within the tank 16 while the tube 10 is refrigerated causing discs or hemispherical pieces of ice 18 to form on the inside of the wall 14 which is preferably made from thin stainless steel.

The pump 2% draws water from the overflow tank 22 wherein water is maintained at the level 24 by means of the float valve 26 and the supply line 28. The pump delivers water into the bottom of the tank 16 at sufiicient volume and pressure to cause the water within the tank 16 to rise to the level 38, thus maintaining a considerable flow of water through the overflow trough 32. The bulk of this overflow water falls into the removable tank 34 though some of it may be carried with the ice and drain to tank 22. It is thus seen that soon after the system is started the removable tank 34 will be filled with water taken 2 to the level 36. When the water level rises to the bottom of the overflow spout 38 water overflows at a rate equivalent to that at which water falls into the, tank 34. One or more drains 39 allows withdrawal of impurities which collect in the bottoms of tanks 16 and 22.-

Overflow water from the tank 34 falls into the water treating cartridge 40 from which any overflow falls directly into the overflow tank 22. Water flows through the cartridge 40 into the cartridge 42 and thence into the overflow tank 22.- Thus most of the water reaches the overflow tank by way of the water treating cartridges, as shown in my co-pending application S. N. 109,942, new Patent No. 2,672,017.

During this circulation of water a portion thereof is frozen within the tank 16 to form the several pieces of ice 18. When one of these pieces of ice has grown to a size such as to affect the control bulb 44 the refrigeration of evaporator 10 is automatically stopped in accordance with the practice taught in my earlier patents. While the method of control is the same, the result of stopping at the desired ice size is different in that the opening of the switch 46 which stops the motor-compressor unit 48 and the pump 20 results in draining the ice maker tank 16 into the overflow tank 22, establishing therein a new water level only slightly higher than the operating water level 24. Since the evaporator 10 not only cools the ice making surface but cools air from the main food space which is free to circulate thereover and may be provided with fins 50 to enhance this action, it will be seen that the evaporator tube 10 Will warm up upon stopping of the system thus causing the pieces of ice 18 to melt free from the wall 14, but instead of immediately floating upwardly as in my previously disclosed ice makers the upper pieces of ice will fall into the water remaining in the bottom of the ice maker tank 16 and remain there until the pump 20 is restarted.

The control which restarts the motor-compressor unit and the pump may be as disclosed in one of my issued patents or pending applications, preferably as shown in my U. S. patent application, Serial No. 50,101, filed September 20, 1948, now Patent No. 2,672,016, with a delayed start of one of the motors, though this delayed start is not so important in a household refrigerator as in the commercial type of ice maker shown in that patent application. In the present case it may be preferred to arrange the thermostatic switch 46 to start the pump motor 52 with a relay switch 53 for delayed start for the motor-compressor unit, thus insuring that the water level in the tank 16 will rise carrying with it the previously released ice before the evaporator 10 is cooled to a temperature which might cause a loose piece of ice to adhere to the wall 14 instead of floating out of the tank as desired.

As the water level rises in the tank 16 and water overflows therefrom to the tank 34 floating pieces of ice are carried out through the overflow trough 32 and slide down the chute 54 to fall into the storage compartment 56 where such ice is supported on the shelf 58. This shelf may be perforated but in any event it fits loosely so that water of meltage from the stored ice falls into the overflow tank 22. It is preferred that at least one hole 60 be provided in the shelf 58 to facilitate its removal to provide access to the float valve 26.

The housing 62 of the ice maker assembly is provided internally with two angle lugs 64 which support it on the studs 66 attached to the top of the refrigerator. It is preferred that the top edge of this housing be fitted with a rubber gasket 68 for the purpose of sealing it against the top of the liner when the nuts on studs 66 are tightened. This eliminates the necessity for providing a separate top for the housing 62.

The water tank 34 is a separate assembly readily removable by sliding forward, carrying with it the selfclosing valve 70 and its trim plate 72 which closes the necessary gap in the front edge of the drip pan 74. This drip pan is also removable but need not be removed in ordinary service operations. It will be noted that the pan 74 is so formed that Water drains to its rear left corner and thence out over the lip 76 which directs the water against the liner of the cabinet at its left rear corner. It is preferred to allow this water to run down the corner of the liner rather than through any tube located inside of the food space or within the insulation as such tubes are notably collectors of dirt and germs. The drip water running down the corner of the liner is directed into the drain 78 pressed into the bottom of the liner and flows through the tube 80 which is straight and easily cleanable to the removable trap 82 and thence to the drip evaporating pan 84 from which it is evaporated with the aid of fabric 86 to room air as described in connection with my patent application, Serial No. 74,528, filed February 4, 1949, now Patent No. 2,709,343. This patent application also discloses the drawer type freezer and mechanism for defrosting its evaporator 20 which is equivalent to the evaporator 88 seen in Fig. l, of the present application. My application, Serial No. 74,528 also shows in Fig. 2 thereof a refrigerant circuit and control device providing hot-gas defrosting of the freezer evaporator. The same system can be used in connection with the present invention, or I can use the one shown by Fig. 4 hereof, which provides for defrosting of the freezer evaporator while the ice-maker evaporator is active.

In Fig. 4 the valve assembly 100 is similar to the assembly 100 of my co-pending U. S. patent application, Serial No. 45,343, filed August 20, 1948, now Patent No. 2,654,227, but is here connected for switching the condenser function from the condenser 101 to the freezer evaporator 88 while allowing the condenser to stand idle and the ice-maker evaporator to continue operating. This provides more rapid defrosting of the freezer evaporator than is obtained by the usual hot-gas" method which connects the compressor discharge directly to the evaporator to be defrosted and leaves the outlet of the evaporator connected with the suction port of the compressor. Such defrosting is inefficient in that no useful work other than defrosting is performed by the compressor and this job is poorly done because the discharge pressure of the compressor drops. I prefer the method shown by Fig. 4 because it utilizes the condensing function of the freezer evaporator being defrosted to deliver liquid refrigerant to the ice-maker evaporator so that both sides of the refrigerating system are being used. Heat given up to the freezer evaporator in defrosting it allows condensation of refrigerant and the evaporation of this refrigerant does useful work in cooling the ice-maker evaporator 10.

In Fig. 4 the solid arrows indicate the flow of refrigerant during normal operation of both the ice-maker evaporator and the freezer evaporator. It will be noted that liquid refrigerant flows from the condenser 101 through the check valve 102 to the restrictor 103 and the ice-maker evaporator 10 from which it must flow through the weighted check valve 104 since the check valve 105 is held closed by the high discharge pressure on its opposite side. After passing the weighted pressure reducing check valve 104 the refrigerant is at a still lower pressure and again it cannot pass through the check valve 106 because of the higher pressure on its opposite side, hence it flows through the freezer evaporator 88 where evaporation is substantially completed and the vapor flows through the tube 107 to the valve assembly 100 and thence back to the suction side of the compressor 48 through the tube 108. This operation continues under control of the thermostatic switch 46, stopping and starting ice-making and ice-releasing cycles with an idle defrosting of the ice-maker evaporator 10 during each ice-releasing period.

The freezer evaporator 88 does not defrost during normal idle periods of the system because it is enclosed in a much colder zone and not subject to any direct heat input. Normally the drawer .110 is open for such short periods that this does not cause evaporator 88 to defrost, but it is only during periods when drawer 110 is open that evaporator 88 can be defrosted by pulling out knob 111, since this knob is so located that closing of drawer 110 pushes it in to deenergize solenoid 112.

When the user opens the freezer drawer 110 and pulls out the knob 111 to defrost the freezer evaporator, as is more fully explained in my co-pending patent application, Serial No. 74,528 above mentioned, current is supplied to the solenoid 112 through the switch 114 causing the armature 116 to lift, carrying with it the four valves attached to it, by means of its stem and the rocker arm 118. Since switch 114 energizes switch 53 to start motor-compressor unit 48 high pressure vapor discharged from the compressor through the tube 120 now flows through the now open port 122 of the valve mechanism as indicated by broken arrow and the tube 107 to the freezer evaporator 88 where it is quickly condensed by the very low temperature of this evaporator while rapidly warming the evaporator to its defrost temperature. Liquid refrigerant collecting in the evaporator 88 cannot flow through the weighted valve 104 which now acts as a check valve but does flow through the tube 124 and the check valve 106 to the inlet of the vapor lock restrictor 103 from which it flows at reduced pressure into the ice-maker evaporator 10. Leaving the ice-maker evaporator largely in vapor phase the refrigerant cannot flow through the restrictor valve 104 because it is being held closed by high side pressure as well as by the weight of the valve, hence vapor leaving the ice-maker evaporator must flow through the tube 126 and the check valve 105 to the valve assembly 100 where it passes through the now open port 128 to the suction tube 108 leading back to the motor-compressor unit 48.

This operation continues until switch 114 is reopened by a timing device 129 as described in my co-pending application Serial No. 74,528, now Patent No. 2,709,343, by thermostatic means associated with the evaporator 88 or manually, as occurs when knob 111 is pushed in either by hand or by the closing of drawer 110. In the copending application last mentioned the timing device stops the defrosting and at the same time releases the drawer to let it close by gravity due to its inclined roller slide. It will be obvious that switch 114 may if desired be opened thermostatically by means of connection with the bulb 130 located adjacent evaporator 88 and this will allow the drawer to reclose as in the co-pending case last mentioned above.

When switch 114 is reopened in any manner the effect is to deenergize solenoid 112 and return the system to normal operation of both evaporators as first described.

Should it be desired to employ the more conventional hot-gas defrost method at the sacrifice of efficiency to obtain a lower cost the single solenoid valve 132 may be connected as shown in Fig. l to allow high pressure vapor to flow from tube 120 to evaporator 88, by-passing 103, 10 and 104. This valve 132 may be controlled by the same switch 114 with manual, thermostatic or clocka'ctuated reclosing as above described.

Since evaporator 88 is normally the coldest part of the system it will have a considerable amount of liquid refrigerant in it at the start of defrosting. Refrigerant cannot flow from it back to evaporator 10 because of valve 104. Flow of vapor to unit 48 is retarded until evaporator 88 approaches the temperature of unit 48, at which time its defrosting will have been completed.

An optional feature is that the timing device 129 of switch 114 or 136 may be energized (wound up) by normal opening of the freezer drawer as well as by pulling out the knob 111. When energized by opening of the drawer alone the defrosting circuit is not closed, hence the effect is merely to cause the drawer to reclose automatically at the end of a predetermined time. When the knob 111 is pulled out some time after the opening of the drawer and to the end of its full travel this closes the defrosting switch 114 or 136 and rewinds the clock mechanism to provide the required defrosting period before the reclosing of the drawer. The partial outward movement of knob 111 which energizes the clock mechanism to time the reclosing of the drawer, with or Without stopping the compressor, but without closing the defrost switch, may be accomplished by mounting the striker 310 on the near side of drawer 110 as shown in Fig. 5. The final outward movement of the drawer thus energizes the clock mechanism. When knob 111 moves back it starts the gravity reclosing o'f drawer 110 and restarts the compressor. In case it is not desired to open the compressor motor circuit each time the drawer is opened, some lost motion is provided between the timing device 129 energized by knob 111 and the switch, as shown by collars 312 which engage the switches after some outward movement of knob 111.

Another optional arrangement is to provide means such as 314 of Figs. 1 and 2 which includes a motor and gear reduction driving a drum or spool on which the tape 316 is wound up to pull the drawer open, the tape being attached to the rear of the drawer, as at 318. This motor is energized periodically through a clock-driven switch or a switch which closes in response to a given number of movements of the drawer to wind up the tape 316 and thus pull the freezer drawer open. Such switches are well known both in the clock-driven variety and in the ratchet-actuated type and have been used for the purpose of defrosting the evaporators of refrigerating systems after a given lapse of time or after a given number of movements of a refrigerator door. I employ such a switch, not only to initiate the defrosting operation, but to energize the motor of 314 and thus cause the tape 316 to open the drawer.

In case the switch is clock-operated the clock mechanism is preferably enclosed within the casing of 314. If the switch is actuated by a ratchet device to operate after a given number of drawer movements this ratchet device may be moved a step at a time by the part 318 engaging the push rod 320 each time the drawer is opened. Alternatively the rewinding of the tape 316 by a spring each time the drawer is opened, as an ordinary steel tape line of the pocket variety is rewound when one presses the button on the tape case, may actuate the ratchet mechanism one notch for each opening of the drawer. In either case the drawer is mechanically opened and the defrosting switch (such as 114 or 136) is closed by the power-actuated winding up of the tape 316. At the end of the defrosting period, the drawer is reclosed, the defrosting switch opened and the refrigeration of the freezer evaporator restarted, as explained in connection with Figs. 4 and 5 hereof and in my copending U. S. application Serial Number 74,528, filed February 4, 1949, now Patent No. 2,709,343.

I claim:

1. In a refrigerator, a non-freezing storage compartment, a freezing storage compartment, a refrigerating system including a pressure imposing element and two evaporators of which one is arranged to cool said nonfreezing compartment and the other to cool said freezing compartment, a condenser forming a part of said system and connected to supply liquid refrigerant for both said evaporators while they are both active as evaporators, and defrosting means arranged to heat the evaporator which normally cools said freezing storage compartment by condensing vapor therein during a period when said non-freezing compartment is being cooled through the medium of said one evaporator and said pressure imposing element draws refrigerant vapor from said one evaporator and also from the first said condenser.

2. In a refrigerator, a non-freezing storage compartment, a freezing storage compartment, a refrigerating system including a pressure imposing element and two evaporators of which one is arranged to cool one of said compartments and the other to cool the other of said compartments, a condenser forming a part of said system and norm-ally connected to supply liquid refrigerant for both said evaporators, and defrosting means arranged to heat the evaporator which normally cools said freeing storage compartment by feeding hot refrigerant vapor to it from said pressure imposing element during a period when the said evaporator which cools the first said compartment continues to cool the same and vapor flows from said condenser to the pressure imposing element.

3. In a refrigerating system, a condenser arranged to supply liquefied refrigerant to a plurality of evaporators while they are simultaneously cooled by the evaporation of refrigerant therein, and means for defrosting one of said evaporators by causing it to serve temporarily as the condenser of said system and to supply liquid refrigerant to the other of said evaporators to cool it while the first said condenser is opened for vapor flow to the suction side of said system.

4. In a refrigerating system installed in a self-contained two-temperature refrigerator, a condenser, a low temperature evaporator, a higher temperature evaporator, means for circulating a refrigerant to cool said evaporators simul taneously, and means for diverting the flow of said refrigerant to cause said low temperature evaporator to act as a condenser while said higher temperature evaporator is cooled by the evaporation therein of refrigerant condensed in said low temperature evaporator which is thereby heated for the purpose of defrosting it and said circulating means draws refrigerant vapor directly from the first said condenser.

5. In a refrigerator, a sub-freezing compartment, 21 refrigerating system including two evaporators of which one is arranged to cool said compartment and the other is operated on a defrosting cycle, and means for defrosting said one evaporator while said other evaporator is active as an evaporator by causing said one evaporator to act as a condenser supplying liquid refrigerant to said other evaporator while the first said condenser is temporarily opened for vapor flow to the suction side of said system.

6. In a refrigerating system employing a volatile refrigerant, two evaporators and a condenser, means for delivering refrigerant vapor to said condenser and refrigerant liquid from said condenser to said evaporators so that said two evaporators are simultaneously cooled, and valve means for diverting the flow of refrigerant in said system to cause high pressure refrigerant vapor to enter one of said evaporators thus causing it to act temporarily as a condenser and liquid refrigerant to flow therefrom to the other of said evaporators so that said other evaporator is cooled while said one evaporator is defrosted, the first said condenser being open to the low side of said system during the defrosting period.

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